Optical (i.e., transport) networks and the like (e.g., Dense Wavelength Division Multiplexed (DWDM), Optical Transport Network (OTN), Ethernet, and the like) at various layers are deploying control plane systems and methods. Control planes provide automatic allocation and management of network resources (e.g., Layer 0, Layer 1, etc. resources) in an end-to-end manner. Example control planes may include Automatically Switched Optical Network (ASON) as defined in ITU-T G.8080/Y.1304, Architecture for the automatically switched optical network (ASON) (February 2005), the contents of which are herein incorporated by reference; Generalized Multi-Protocol Label Switching (GMPLS) Architecture as defined in IETF Request for Comments (RFC): 3945 (October 2004) and the like, the contents of which are herein incorporated by reference; Optical Signaling and Routing Protocol (OSRP) from Ciena Corporation which is an optical signaling and routing protocol similar to Private Network-to-Network Interface (PNNI) and MPLS; or any other type control plane for controlling network elements at multiple layers, and establishing connections therebetween. Control planes are configured to establish end-to-end signaled connections such as Subnetwork Connections (SNCs) in ASON or OSRP, and Label Switched Paths (LSPs) in GMPLS and MPLS. Control planes are configured to compute paths, to route/signal the SNCs/LSPs, and program the underlying hardware accordingly.
Retain Home Path (RHP) is a feature in a control plane related to restoring a connection and is described, for example, in commonly assigned U.S. Pat. No. 9,088,486, issued on Jul. 21, 2015, and entitled “Retention of a sub-network connection home path,” the contents of which are incorporated by reference herein. The RHP feature reserves the resources of a home path while a connection (e.g., SNC, LSP, etc.) (also, a connection can be referred to as a service) is not fully provisioned on all or part of the home path. The home path is defined as the original path and the connection can be off of the home path for a variety of reasons, e.g., protection, maintenance, etc. Thus, the RHP feature reserves resources on the home path to provide reliability and consistency, allowing a connection to revert when possible to the home path.
In the case of Layer 0 (L0) photonic and Layer 1 (L1) Time Division Multiplexing (TDM), the service characteristics can be modified “on the fly” such as for flex grid resizing at L0, Optical Data Unit flexible (ODUflex) resizing, or modification of other service characteristics. Disadvantageously, any modification while the connection is off of the home path can lead to a discrepancy between the current route and the reserved home path.